Re: Purple Boxes

["Dave Emery" <die@pig.die.com>]

 Lucky Green writes :
> 
> In article <199508152206.SAA23244@acmex.gatech.edu>,
> gt7508b@prism.gatech.edu (PHrEaK!) wrote:
> 
> >Does anyone know of sources for des chips???
> >Are there any public key chips out there???
> >Has anyone ever tried putting PGP on a chip??? RSA??? (Are these too
> >slow for realistic real time hardware voice/data encryption??)
> >I know a little about digital electronics (I am a computer engineering
> >student) and I would love to get some data books and see if I could
> >come up with a secure "encryption box" that people could build.
> 
> I don't know off the top of my head who makes DES and RSA chips.  I am
> sure there are many manufactors of DES chips. Try TI, National, and
> Motorola. I belive that Schneier has a list of RSA chip makers.
> 
	I'm quite convinced that with a fast microcontroller and
especially a really fast DSP engine you can do both 3-DES and idea in
the same hardware that does the rest.  You need only to encrypt
somewhere between 9.6 kbits and 16 kbits per second or between 1 and 2
kbytes/sec or 125 to 250 block encryptions per second which is lots less
than 100+ kbytes/second people have been getting for DES file encryption
on high end PC class processors.  And a good DSP core carefully
programmed is probably quite comparable to the performance of a DX-4 or
mid range Pentium on algorithms such as DES, idea or even RC4. 

	I should think realistically there should be a lot of bandwidth
left over for the voice compression - for the encryption you might
possibly be talking 5% of the dsp cpu if you use a 50 mhz part.

	And while RSA is nice, it has usually been confined to key
exchange because it so slow.   There are hardware versions of RSA
that will work at modem speeds or better with reasonable moduluses
but this is specialized VLSI hardware and as far as I have ever noticed
is not available cheaply as is the kind of DSP used for V.34 modems.
And certainly doing key exchange RSA on a dsp or 32 bit microcontroller
is reasonable if it only adds a second or two of call setup.

> For the DSP part of a "bump in the cord" encrytion box, you want to get
> the "TI TMS320 Family Development Support" booklet by calling (800)
> 477-8924. You also want to look at Motorola's 68000 CPU, DSP, and
> controller on one chip. I can't recall the exact product number. Just call
> Motorola and ask for it.
> 

	I reiterate my suggestion of a few months ago that
one could quite easily adapt the firmware on one of the new simultanious
data and digital voice on the same phone line modems to incorperate
encryption, and quite possibly encryption/key exhange interoperable
with some mode of PGPphone.   Doing this would relieve one of the
need to develop or manufacture any hardware at all - all that would
be required to have a portable "bump in the cord" encrypter widely
available for a low price would be creating a new version of the
downloadable flash ROM image that did encryption and PGPphone
key exchange.

						Dave Emery

						die@die.com